1. Field of the Disclosure
The present disclosure relates to a flexible display device, and particularly, to a flexible display device capable of preventing disconnection or short-circuiting of wires that may occur at a bending area during a bending process for a minimized bezel width, in an organic light-emitting diode display manufactured using a flexible substrate, and a method for fabricating the same.
2. Description of the Related Art
Among flat panel display devices proposed to replace the conventional cathode ray tube, an organic light-emitting diode (OLED) display has a characteristic that a light-emitting diode provided at a display panel has high brightness and a low operation voltage. Such OLED display has advantages that a contrast ratio is large because it is a spontaneous light-emission type, and a very thin display can be implemented. The OLED display can easily implement moving images because a response time is several micro seconds (μs). Further, the OLED display has an unlimited viewing angle, and is stably operated even at a low temperature.
In the OLED display device, display devices are formed on a substrate such as glass. Recently, a flexible organic light-emitting diode (OLED) display device, which is capable of maintaining a display function even when rolled (or bent) like paper due to its flexible material such as plastic or metal foil rather than a non-flexible substrate, has been developed.
FIG. 1 is a planar view schematically illustrating a flexible organic light-emitting diode (OLED) display device in accordance with the conventional art, and FIG. 2A is an enlarged view of part ‘A’ in FIG. 1.
Referring to FIGS. 1 and 2A, the conventional flexible OLED display device 1 is formed on a flexible substrate 10 including an active area (A/A) and a non-active area (N/A).
The active area (A/A) is a region where an image is substantially displayed. A plurality of pixels (P) are arranged in the active area (A/A), in the form of matrices. Each of the pixels (P) includes a switching transistor (ST1), a driving transistor (DT), a sensing transistor (ST2), a capacitor (C), and an organic light-emitting diode (OLED).
The switching transistor (ST1) of the pixel (P) is connected to a gate line (GL) and a data line (DL) which are formed in the active area (A/A) so as to cross each other. The driving transistor (DT) is connected to a driving voltage line 14b for supplying a driving voltage (VDD) to the pixel (P) in the active area (A/A). The sensing transistor (ST2) is connected to a reference voltage line 14a for supplying a reference voltage (Vref) to the pixel (P) in the active area (A/A).
The non-active area (N/A) is a region formed around the active area (A/A), and is covered by a bezel portion, etc. Driving circuitry for driving the pixels (P) in the active area (A/A) and wires may be formed in the non-active area (N/A).
The driving circuitry includes a data driving portion 20, a gate driving portion 13 and a light-emitting controller (not shown). The data driving portion 20 is mounted at a lower end non-active area (N/A) in the form of a chip. The gate driving portion 13 and the light-emitting controller are formed at one or more sides of the non-active area (N/A), in the form of a gate in panel (GIP).
Wires include power lines 14a˜14c, and signal lines GSL, DSL. The power lines 14a˜14c includes a driving voltage line 14a, a reference voltage line 14b and a ground line 14c. Also, the signal lines GSL, DSL include a gate signal line (GSL), a data signal line (DSL) and a light-emitting signal line (not shown).
The driving voltage line 14a outputs a driving voltage (VDD) provided from the data driving portion 20 to the pixel (P) in the active area (A/A). The reference voltage line 14b outputs a reference voltage (Vref) provided from the data driving portion 20 to the pixel (P) in the active area (A/A). The ground line 14c outputs a ground voltage (GND) provided from the data driving portion 20 to the pixel (P) in the active area (A/A).
The driving voltage line 14a, the reference voltage line 14b and the ground line 14c include a region vertically extending from the data driving portion in the lower end non-active area (N/A), and a region formed in parallel to the data driving portion 20.
That is, the driving voltage line 14a, the reference voltage line 14b and the ground line 14c are extending from the data driving portion 20 in a vertical direction, at a region adjacent to the data driving portion 20 in the lower end non-active area (N/A). The driving voltage line 14a, the reference voltage line 14b and the ground line 14c are formed as bars, in parallel to the data driving portion 20, at a region adjacent to the active area (A/A) in the lower end non-active area (N/A).
The gate signal line (GSL) outputs a gate signal provided from the data driving portion 20 to the gate driving portion 13. The data signal line (DSL) outputs a data signal provided from the data driving portion 20 to the data line (DL) in the active area (A/A). The light-emitting signal line outputs a light-emitting signal provided from the data driving portion 20 to the light-emitting controller.
In accordance with one embodiment, these wires may be formed to cross each other at least once, in the lower end non-active area (N/A). Thus, the power lines 14a˜14c and the signal lines GSL, DSL are formed on different layers, in order to prevent short-circuiting when the wires cross each other.
In the conventional flexible OLED display device 1, the lower end non-active area (N/A) is formed to have a larger width than the rest of the non-active area (N/A). A bending area (B/A) is formed in the lower end non-active area (N/A), and part of the lower end non-active area (N/A) is bent to a rear surface of the flexible OLED display device 1. Under such configuration, the width of the lower end non-active area (N/A) can be reduced.
FIG. 2B is a cross-sectional view of the flexible OLED display device of FIG. 1, which illustrates a bent state.
Referring to FIG. 2B, reference numeral 11 denotes an organic light-emitting diode (OLED) formed in an active area (A/A), and reference numeral 12 denotes an encapsulation layer for encapsulating an OLED.
Referring to FIG. 2B, in the conventional flexible OLED display device 1, the lower end non-active area (N/A) is bent based on a bending area (B/A), so that part of the lower end non-active area (N/A) can be positioned on a rear surface of the flexible OLED display device 1. A curvature radius (R) of the bending area (B/A) is about 0.3 mm.
As mentioned above with reference to FIG. 2A, in the lower end non-active area (N/A) of the conventional flexible OLED display device 1, wires are formed to cross each other. Thus, the power lines 14a˜14c and the signal lines GSL, DSL are formed on different layers.
However, because the wires are formed to cross each other even in the bending area (B/A), the wires may be disconnected from each other due to bending stress in the bending area (B/A).
FIG. 3 is a cross-sectional view taken along line in FIG. 2B.
Referring to FIG. 3, the signal lines GSL, DSL and the power lines 14a˜14c are formed on different layers to thus be insulated from each other.
For instance, a gate signal line (GSL) and a data signal line (DSL) are formed on a flexible substrate 10 with a distance therebetween. A first insulating layer 15 is formed on the gate signal line (GSL) and the data signal line (DSL).
A driving voltage line 14a and a ground line 14c are formed on the first insulating layer 15 with a predetermined gap therebetween. The driving voltage line 14a and the ground line 14c are formed to overlap the gate signal line (GSL) and the data signal line (DSL), respectively. A second insulating layer 16 is formed on the driving voltage line 14a and the ground line 14c. 
When the bending area (B/A) is bent with more than a predetermined curvature radius, cracks/breaks may occur at wires due to bending stress as shown in FIG. 3 (indicated by “a” and “b”). This may cause the wires to be disconnected from each other, or the insulating layer may be damaged to cause short-circuiting of the wires.
Such disconnection or short-circuiting of the wires may cause a malfunction of the flexible OLED display device 1.